1. Field of the Invention
This invention relates to dynamoelectric machines having stator members with multilooped coils disposed therein, and more particularly to a system for bracing stator end region peripheral connecting ring segments which electrically connect individual coil sides to form the coils.
2. Description of the Prior Art
Large dynamoelectric machine designs have evolved which use a stator winding of complex shape to handle the voltages and currents required by loads imposed on modern power generation systems. The large number of slots formed in a typically tubular stator core, the use of parallel windings in each phase, and multiple loop coils per phase necessitate the use of a complicated end connection scheme for electrically joining slot-disposed coil sides into a stator winding. Such connection scheme conforms to a restricted space, provides rugged construction, and allows necessary connections between stator coil sides.
The present solution to this problem consists of an end basket made by weaving together "diamond"-shaped coil loops. Each loop on the multiple loop coil is constructed from two coil sides each of which consists of a straight portion that extends the length of the stator slots and a complicated curved, end turn portion at each end thereof. Multiple coil sides are usually disposed in each slot in top (radially inner) and bottom (radially outer) positions. The coil sides of each loop are disposed in different positions in separate slots. This end turn portion has a complex shape which bends axially, radially and circumferentially. The manufacturing of the coil sides requires a three-dimensional form (typically of wooden construction) against which the copper coil sides are bent and twisted to form the end turn portions. The stator coil sides are woven together in the end turn regions to form "diamond"-shaped coils to provide an end basket structure.
Such end basket structure provides the necessary stator coil side connections in a reasonably compact and rugged structure. The support system for the diamond-shaped coils included triangular-shaped blocks of an insulating material such as Micarta which were laced to parallel phase rings disposed at one end of the machine. The support for the end turn windings was provided by maintaining resin-impregnated pads in compressive engagement between the blocks and the coil side end turn portions. One of the major disadvantages of this end basket structure is that the coil side interweaving of the "diamond"-shaped coil loops makes it impossible to remove a single coil side from the bottom of a stator slot without removing from twelve to eighteen of the adjacent top coil sides which block its removal in the end region.
When field repair or replacement of a bottom stator coil side in such a dynamoelectric machine is necessary, many top coils in the vicinity of the to-be-repaired bottom coil side must also be removed to access the bottom coil side. Removal of the top coil sides is a costly and tedious process considering the fact that the repair is usually done in the field. The coil side removal process also requires disassembly of the micarta bracing and resin impregnated pads associated with the coil sides. In this process of unbracing the machine and removing coil sides the machine is especially vulnerable to additional damage. Once the machine is disassembled and repaired, the coil sides must be reinserted in the slots and the micarta blocks and resin-impregnated pads must be reshaped and reassembled under field conditions.
In copending application by Mr. L. J. Long having Ser. No. 139,083, filed on Apr. 10, 1980, and assigned to the assignee of this application, there is disclosed a dynamoelectric machine which has a stator winding comprising a plurality of stator coil loops each of which includes two straight coil sides which run the entire length of the stator slots and extend rectilinearly into the end region. A generally circular connector ring segment passes between stator slots in an end region of the stator and connects the two straight coil sides to form a complete coil loop. The connector ring segment is typically constructed to the same specification as is the stator coils.
The dynamoelectric machine disclosed in the aforementioned application has a stator core and a plurality of coils constituting a stator winding disposed in the stator core. Each of the coils includes two coil sides that extend a predetermined axial distance from the core and a connector ring segment which joins the coil sides to form a complete coil loop. The length of the two coil sides varies with the coil loop so that commonly slotted coil sides are of different lengths and the potential for interference between adjacent connector ring segments is minimized. The resulting peripheral connector ring segments together provide a generally cylindrical structure on both axial ends of the stator.
Disclosed herein is a mounting bracket that provides effective support for all connector ring segments while allowing easy removal of any selected connector ring segment. Each mounting bracket generally comprises a foundation structure which is cantilevered from each end of the stator and a plurality of spacers which are attached to the foundation structure. A plurality (the number depending on the size of the stator) of mounting brackets are joined to each axial end of the stator at selected circumferential positions. Each foundation structure constitutes a base portion and spacer support leg portions which extend perpendicularly from the base portion from each axial end thereof. The spacers are assembled with the connecting ring segments and are attached to the foundation structures by fastener means which extend through each spacer and the spacer support leg portions. Fastener means such as screw bolts provide retention of the spacers and connector ring segments to the foundation structures.
The disclosed mounting bracket for bracing end turn connector ring segments has the following advantages over prior art end turn support structures:
(1) A stator coil end turn structure that is more rugged than the prior art;
(2) Readily assembleable and disassembleable spacers for reducing the installation or repair time for the peripheral connector rings segments and/or coil sides;
(3) Increased stator coil rigidity over that of the prior art bracing system; and
(4) Augmentation of the bracing for the stator coil sides.